(1) Field of the Invention
The invention relates to an oil well jack which depends on hydraulic pressure applied through actuators to move a walking beam, and a high degree of amplitude and frequency control of the walking beam is provided through a novel hydraulic valve system.
(2) Description of the Prior Art
Many prior art systems for pumping oil are known, and most of them depend for operation upon a prime mover such as an internal combustion engine or an electric motor driving a walking beam through a complex series of mechanical gears. While this system may be adequate when the motion and speed of the beam is predetermined and does not change, still, if the length of beam stroke or the speed of the beam is to be changed the gears must be changed; which operation requires two or three days work by skilled jack mechanics, and results in substantial down-time of the expensive equipment and lost product production. The oil well jack to be described hereinafter offers the user a very versatile system wherein both length (amplitude) of the walking beam stroke may be changed and the speed of motion (frequency) of the beam may be changed by relatively simple adjusting means. An unexpected and unobvious result of the invention disclosed herein is the fact that a complete jack constructed according to this disclosure can be delivered to the pumping site for approximately one half the cost of the conventional gear-driven jack. It follows, then, that the reduced initial cost plus a high level of flexibility in operation has reslted in commercial success of the system.
Applicant is aware of the following prior art U.S. patents:
______________________________________ Galbraith 867,578 Tozier 1,233,728 Junggren 1,133,288 Burgess 3,419,246 Austrian Patent 191,565 Delitsch 1,789,353 Carson 1,806,447 Freeman 2,647,534 Terry 3,015,963 French Patent 1,335,138 ______________________________________
Galbraith, Tozier, Burgess, and the Austrian Patent appear to teach that it is well known to use the pivotal movement of a lever arm to cause longitudinal movement of a valve.
Delitsch, Carson, Freeman, Terry and the French Patent show spring biased valves. Junggren shows a valve actuator moved against a biasing spring by a pivoting beam member and having a cam structure to positively close the valve in the event of prolonged open-state operation.
None of the patents discussed above appears to teach or even suggest the system as claimed in this application.